The declarations outside the global scope were being skipped in this
transformation, but if the initializer of a declaration referenced a
uniform struct that's being replaced, it should have been visited too.

Bug: chromium:1204861
Change-Id: Ie2a743126c785eb7d6e3542ba80faa4defc3509f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2889598
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>